Granulator with sound absorbing housing

ABSTRACT

A granulator-hopper combination has a housing which is formed with double walls forming an open air space therebetween. Openings through the inner wall place the housing interior in communication with the air space, whereby this housing acts as a volume resonating muffler.

United States Patent DeNoyer Aug. 26, 1975 GRANULATOR WITH SOUND ABSORBING 7 HOUSING Primary Examiner-Stephen J. Tomsky Assistant Examiner-Vit W. Miska [75] lnvemor' Donald DeNoyer Belon Attorney, Agent, or Firm-Dirk J. Veneman; Bruce L. [73] Assignee: Beloit Corporation, Beloit, Wis. Samlan; Gerald A. Mathews [22] Filed: May 20, 1974 [21] Appl. No.: 471,793 [57] ABSTRACT 521 US. Cl 181/33 K; 181/33 1.; 241/100; A granulatovhopper combination has a housing which 241/186 R is formed with double walls forming an open air space [51] Int. Cl. E04b l/99; GlOk 11/04 therebetween. p ng hr gh the inner wall place 53 Fi l of Search 241 100 1 23 30 the housing interior in communication with the air l8l/33 K, 33 D, 33 L space, whereby this housing acts as a volume resonating muffler. [56] References Cited UNITED STATES PATENTS 14 Claims, 7 Drawing Figures 3,866,708 2/1975 Rudszinat 181/33 K l 1) 37) )1 v v i 28 v 1, Q 26 l i lc v Q I u I lo I I llb 3 1, 34 1 r I I I I I I] II SHEET 1 BF 3 3.901349 sum 2 UF 3 PATENTED AUG 2 6 I975 O c C OOOOOOOOOO OOOOOOOOO OOOO OOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOO A OOO UOOOO OOOOOOO OOOOOOOOOOOM O WMV 0 000 0 0 00 0 nm O O wmv 00000 000 000000 M O O O OO O OO W O OO WWMV O O O O 0000 00000000000 000000 000000 WW O W O WW O O A V O O O O O mWW O W n v O O mv muw O 0000 OOOOOO 0000000000000 0000000000000.

0000000 000000000 OOOOOO 0000000000000. 0000000 000000080 0000 OOOOOOOOOOOO 0000 00000000 000000 000 OOOOOOOOOOOO OOOOOOOOOOOOOOOO 000000000000 00 0000000000000 0000000000 00 OOOOOOOOOOOO 000000000 O00 O00 000 00 00000000. 000 000000 00000 00000 0000 w 0000. O0 OOOQ GRANULATOR WITH SOUND ABSORBING HOUSING BACKGROUND OF THE INVENTION This invention relates to grariulators, and it relates in particular to the problem of the sound proofing thereof.

Granulators that are used to chop up or comminute plastic materials create a great deal of noise since many of the plastics used today are very tough, and when they are comminuted, the cutting action is very noisy due to the kind of knives used. In addition, due to the rotary action of the cutting means, hard particles of plastic are thrown with some force against the steel walls of the machine with resulting noise.

In addition, it has been known that material such as clay and epoxy coatings on metal, soft metals such as lead and aluminum, and the foamed plastics all have an ability to absorb or attenuate sound impinging thereon to some degree. Such materials have been used, but it has been found that when so used in what would be considered the normal manner, the noise level of the machine was reduced but not sufficiently to have much significance. A major portion of noise created in the interior of a noisy granulating machine will exit from the opening in the machine amounting to only small percent of a covering for the machine. This factor creates the problem of how to feed scrap material into machines which have noise suppression hoods associated therewith, because feeding the materials into the machine must be done through an opening, with the result that interior noise will escape through the feed opening. Using screens to mask the feed opening will help, but is not enough.

One attempt to make a sound proof housing comprises making the hopper section out of a double walled construction, said double walls forming therebetween an airtight space which it is believed provides increased soundproofing. Such an arrangement is shown for example in the Peterson US. Pat. No. 3,743,880. However, there exists a continuing need for further improvements to further reduce the level of noise emanating from this type of machine.

SUMMARY OF THE INVENTION Thus, it is a purpose of the present invention to overcome the disadvantages of previously known arrangements by providing a granulator having means for greatly reducing the level of sound emanating therefrom.

This purpose of the present invention is achieved by constructing the housing so that the housing itself becomes a volume resonating muffler operating on the principle ofa Helmholtz resonant cavity. Such resonant cavities have been known heretofore for muffling noises in many different uses, one of these being for example the conventional automobile muffler. However, such conventional uses do not suggest the application of this principle to a device such as a granulator. The sound waves of the noises to" be muffled are contained within the interior of the granulator as much as possible. Such containment is achieved by providing an impedance mismatch near the feed opening of the granulator such that most of the sound waves generated are reflected back into the interior of the granulator. The housing is formed with inner and outer walls forming an air space therebetween. Openings are provided through the inner wall, placing the air space into communication with the interior of the granulator. The air space then acts as a resonant cavity or volume which in combination with the openings provides the impedance mismatch which causes sound waves to be reflected back into the interior. In addition, the resonant volume dissipates the sound waves in two ways. First, the resonant volume will absorb energy from the sound waves that causes the volume to resonate and secondly sound waves emanating from the resonant volume and directed back into the interior of the granulator will interfere with sound waves of the same frequency in the said interior.

Granulators of the type with which the present invention is concerned are generally constructed with a housing forming a hopper extending upwardly and outwardly from the cutting chamber of the granulating mechanism. A feed entrance opens into the upper part of the hopper, preferably in a horizontal direction. In a preferred arrangement of the present invention, the said openings communicating the interior of the granulator with the resonant volume are located in the vicinity of the feed entrance.

According to one embodiment of the invention, the housing portion forming the hopper and its feed entrance is formed with two walls of essentially similar shape, the outer one being larger than the inner one so as to form therebetween the said air space.

In accordance with another embodiment of the invention, only the inner wall is formed as a hopper, this inner wall being completely surrounded by a box-like enclosure which is completely enclosed so as to form with the inner wall an enclosed air space which acts as the volume resonating cavity. This latter embodiment has the additional advantage that the entire granulating mechanism including motors and the like can be completely isolated from the floor, for example through vibration isolating elastomeric mountings, so that it is possible to even eliminate sound transmission paths to the floor through bolts or the like.

Thus, it is an object of the present invention to provide a granulator having new and improved sound absorbing capabilities.

It is another object of this invention to provide a granulator wherein the housing thereof is itself constructed as a sound muffler.

It is still another object of this invention to provide a granulator having a double wall construction, the space between the walls acting in combination with openings through the inner wall as a sound muffler.

It is still another object of this invention to provide a granulator having a double wall construction serving as a sound muffler, the inner and outer walls being of similar shape and forming the hopper.

It is still another object of this invention to provide a granulator having an inner wall in the shape of a hopper and an outer wall in the form of a box-like enclosure, these two .walls being interconnected so as to form therebetween a volume resonating cavity.

Other objects and advantages of the present invention will become more apparent from the detailed description to follow, together with the accompanying drawings,

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in considerable detail together with the accompanying drawings which are provided for purposes of illustrating the preferred embodiments.

FIG. 1 is a perspective view of a granulator including the features of the present invention.

FIG. 2 is a cross-sectional view of the upper portion of FIG. 1, taken in a vertical plane through the line 22 of FIG. 1.

FIG. 3 is an enlarged view of a portion of FIG. 2, taken along line 3-3 of FIG. 2.

FIG. 4 is a side elevational view of a granulator constructed in accordance with another embodiment of the present invention, the upper right-hand portion of FIG. 3 showing a central section therethrough and the cover having been broken away at the lower left-hand portion to reveal the interior structure thereof.

FIG. 5 is a perspective view of the embodiment of FIG. 4 with a portion thereof cut away to show the frame structure.

FIG. 6 is a greatly enlarged view of the portion of FIG. 3 designated therein by the letter A.

FIG. 7 is an enlarged partial cross-sectional view taken along line 7-7 of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, like elements are represented by like numerals throughout the several views.

Referring to FIGS. 1 and 2, there is shown a granulator housing in the form of a hopper 12 having an entranceway 10 with a feed opening 11 at one end thereof. The lower portion of the hopper 12 at least partially surrounds a cutting chamber 13 having therein a cutting mechanism 13a which comprises a rotary blade mechanism, only the outline of which is shown in dotted lines in FIG. 2, this mechanism being rotatable about an axis 13b. A curtain 11a of a suitable material such as neoprene covers the feed opening 11 partially to prevent the escape of noise and partially to prevent material from being thrown back through the feed opening. Another curtain 11b is provided farther into the entranceway 10. These curtains can be pushed inwardly about their upper mountings 110 for feeding material into the hopper.

The granulator includes a base 14 which would hold the cutting mechanism 13a as well as a motor 18 which drivingly engages the cutting mechanism via a transmission element, for example a V-belt 19, a portion of which is visible in FIG. 1. The regrind material is received in a suitable collecting bin within the base 14, access to which may be provided by opening the door 15 at the front of the base. Access to the cutting mechanism for changing blades or the like is provided by rotating the entire hopper 12 about pivot axis 16 in the direction indicated by arrow 17.

In accordance with the main feature of the present invention, the hopper 12 is constructed in such a manner that it forms a sound absorbing muffler. This is accomplished in the embodiment of FIGS. 1 and 2 by constructing the hopper 12 with an inner wall 26 and an outer wall forming therebetween an enclosed, but not airtight air space 28. A sound absorbing layer 27 is provided on the interior of the outer wall 25. This layer may be formed for example of open cell acoustical polyurethane foam, Baryfol or the like, preferably of a thickness of about one inch. A liner might also, but not necessarily be formed on the outer surface of inner wall 26. The inner wall in the vicinity of entranceway 10 includes perforations 30 which are so arranged so that sound waves passing through the entranceway 10 enter the air space 28 thereby reducing the sound level in accordance with the Helmholtz principle described above. In this embodiment, outer wall 25 with liner 27 is similar in shape to and completely surrounds inner wall 26 and is connected thereto by suitable braces (not shown). While the perforations can be placed at any location, it has been found particularly advantagous to provide the perforations in the ceiling of the en tranceway 10 adjacent the entrance 1 1. Also, while the size, number and spacing of the holes will vary, in one particular embodiment in which the cutting mechanism is 8 inches in length and has an 8 inch diameter cutting circle it has been found suitable to use holes of approximately one eighth inch diameter with their centers spaced apart by approximately three sixteenths inches, and the spacing of the holes being as shown in FIG. 3. In this embodiment the holes would cover the entire square area of FIG. 3, although for simplicity only some of these holes are actually shown.

FIGS. 4 through 7 illustrate another embodiment of the invention. Within an outer box-like structure 40 there is provided a granulator device 39. This granulator device is similar in many respects to the device shown in FIGS. 1 and 2 with the following exceptions. Firstly, the device 39 has only a single wall hopper 39a rather than a double wall construction and the feed entranceway is extended relative to the FIG. 1 embodiment as shown at 42. The base 45 is somewhat larger and a motor 46 is mounted somewhat differently than the motor 18.

The granulator device 39 includes a pair of curtains 44a and 44b mounted at 44 adjacent the feed opening 43 and slightly inwardly thereof, respectively. These are similar to the curtains 11a and 11b of FIG. 1. In this case the cutting mechanism 41 is driven by a suitable V-belt 47 from the motor 46.

In accordance with the main feature of the present invention, the granulator of FIGS. 4 through 7 is constructed as a sound absorbing muffler by providing an inner wall and an outer wall construction with an air space therebetween similar to the embodiment of FIGS. 1-3. In this case, however, the granulator device 39 itself forms the inner wall. The outer wall is provided by the box-like structure 40 erected around the granulator device 39. This box-like structure may comprise a floor panel 60 on which are mounted four vertical corner posts 51 (one of which is visible in FIG. 5) and wherein the tops of these corner posts are interconnected by suitable frame members 52. The box-like structure would be closed off by suitable panels such as a top panel 53, side and back panels 54,- a front top panel 55 providing an opening therein for feed opening 43 and a front bottom panel 56. All of these panels should be removable without too much difficulty for servicing the granulator device 39. Where removal would be most frequent such as for removing regrind material, the relevant panel, in this case the front lower panel 56 could be mounted on hinges 57 with a suitable handle 57a. The other panels can be conveniently mounted with bolts 58 connecting the panels to the frame members 51 and 52.

A suitable sound attenuating liner 59 can be mounted on the inside of the panels, this liner being similar to the liner 27 in FIGS. 1 and 2.

FIG. 6 illustrates in greater detail the connection of the entranceway 42 to the front panel 55. Angle irons 49 would be welded to the exterior of the entranceway 42. The opening in panel 55 adjacent the feed opening 43 would be greater than the outer dimensions of the entranceway 42 while the liner 59 attached to the panel 55 would more closely approximate the outer dimensions of the entranceway 42 so that the material of liner 59 abuts the entranceway 42 and also the angle iron 49.

The advantage of this particular construction is that at the feed opening 43 the metallic elements of granulator 39 are free of contact with the metallic portion of box-like structure 40, in this case referring to the panel 55. Vibration isolation of the granulator device 39 is further provided by vibration isolating shear mountings 62 which separate the entire structure 39 from the boxlike structure 40 via elastomeric mounting. One of these is shown in greater detail in FIG. 7 and includes an upper bracket 63 connected to the base 45 of the granulator, lower brackets 65 connected to the lower panel 60 of the structure 40 and intermediate shear blocks of rubber or another suitable elastomeric material interconnecting the brackets 63 and 65. Because of this arrangement which completely vibration isolates the granulator device 39 from the box-like structure 40, sound transmission to the floor through common sound transmission means such as bolts and the like are even eliminated.

In accordance with a main feature of the present invention, the inner wall of the present embodiment includes perforations 48 in the ceiling of the entranceway 42, these openings communicated with the air space between device 39 and box-like structure 40 so as to provide communication therewith for the passage of sound waves for attenuating sound in accordance with the Helmholtz principle as described above.

One advantage of the present arrangement, especially in comparison with the previous arrangement with an airtight space between the inner and outer walls, is that since the space need not be airtight, it is possible to run ducts into interior of the apparatus for ventilation or the like. As an example, ducts 29 and 31, each having a lining 59 on the inside thereof, as shown in FIGS. 4 and 7 is provided for respectively delivering cooling and/or ventilation air to and exhausing air from the space between 39 and 40. A main purpose for this airflow would be to cool the motor 46. A blower, indi cated schematically at 33 may optionally be provided to enhance airflow.

' Although the invention has been described in considerable detail with respect to a preferred embodiment, it will be apparent that the invention is capable of numerous modifications and variations apparent to those skilled in the art without departing from the spirit and scope of the invention.

I claim:

1. A granulator comprising: a housing, a granulating means within the housing, said housing having an entrance means for introducing therein material to be granulated, and at least a portion of the housing comprising a double wall including inner and outer walls forming an air space therebetween, and perforations in the inner wall placing the interior of the housing into. open communication with the air space, said perforations being arranged such that at least some of the sound waves passing through are reflected back into the interior of the housing to interfere with newly emitted sound waves-of the same frequency, so as to function as a volume resonating muffler.

2. A granulator according to claim 1, including duct means passing through the outer one of said double walls of the housing for introducing air into or removing air from said air space.

3. A granulator according to claim 1, said housing forming a hopper above the granulating means and said entrance means comprising a feed opening into the upper part of the hopper, said perforations being located at least in the vicinity of said feed opening.

A granulator according to claim 1, said inner wall forming a hopper having a lower section which is adjacent to a portion of the granulator means and an upper section extending upwardly from the lower section, the outer wall comprising a box-like structure completely surrounding the said inner wall to form therewith said air space, and an entranceway extending outwardly through the box-like structure.

5. A granulator according to claim 3, said double walled part including the entire hopper.

6. A granulator according to claim 3, said feed opening communicating with an entranceway extending horizontally into the upper part of the hopper, and including at least one movable curtain covering said feed entrance.

7. A granulator according to claim 3, the entire hopper section being of said double walled construction, the inner and outer walls being of similar shape throughout and spaced apart to form said air space which is of essentially uniform thickness throughout.

8. A granulator according to claim 7, the inner and outer walls being metal.

9. A granulator according to claim 8, including a layer of synthetic sound attenuating material lining the interior of the outer wall.

10. A granulator according to claim 4, including a base, said granulating means and said hopper mounted on the base, a motor means mounted on the base for driving the granulating means, and said box-like enclosure also enclosing said base.

11. A granulator according to claim 10, including mounting means for attaching the base to the box-like structure so as to be vibration isolated therefrom.

12. A granulator according to claim 4, the inner and outer walls being of metal and including a layer of synthetic sound attenuating material on the interior of the box-like structure.

13. A granulator according to claim 11, said mounting means including elastomeric shear mountings interconnecting the bottom of the base to the bottom of the box-like enclosure.

14. A granulator according to claim 4, said box-like enclosure including a frame and panels removably attached to the frame. 

1. A granulator comprising: a housing, a granulating means within the housing, said housing having an entrance means for introducing therein material to be granulated, and at least a portion of the housing comprising a double wall including inner and outer walls forming an air space therebetween, and perforations in the inner wall placing the interior of the housing into open communication with the air space, said perforations being arranged such that at least some of the sound waves passing through are reflected back into the interior of the housing to interfere with newly emitted sound waves of the same frequency, so as to function as a volume resonating muffler.
 2. A granulator according to claim 1, including duct means passing through the outer one of said double walls of the housing for introducing air into or removing air from said air space.
 3. A granulator according to claim 1, said housing forming a hopper above the granulating means and said entrance means comprising a feed opening into the upper part of the hopper, said perforations being located at least in the vicinity of said feed opening.
 4. A granulator according to claim 1, said inner wall forming a hopper having a lower section which is adjacent to a portion of the granulator means and an upper section extending upwardly from the lower section, the outer wall comprising a box-like structure completely surrounding the said inner wall to form therewith said air space, and an entranceway extending outwardly through the box-like structure.
 5. A granulator according to claim 3, said double walled part including the entire hopper.
 6. A granulator according to claim 3, said feed opening communicating with an entranceway extending horizontally into the upper part of the hopper, and including at least one movable curtain covering said feed entrance.
 7. A granulator according to claim 3, the entire hopper section being of said double walled construction, the inner and outer walls being of similar shape throughout and spaced apart to form said air space which is of essentially uniform thickness throughout.
 8. A granulator according to claim 7, the inner and outer walls being metal.
 9. A granulator according to claim 8, including a layer of synthetic sound attenuating material lining the interior of the outer wall.
 10. A granulator according to claim 4, including a base, said granulating means and said hopper mounted on the base, a motor means mounted on the base for driving the granulating means, and said box-like enclosure also enclosing said base.
 11. A granulator according to claim 10, including mounting means for attaching the base to the box-like structure so as to be vibration isolated therefrom.
 12. A granulator according to claim 4, the inner and outer walls being of metal and including a layer of synthetic sound attenuating material on the interior of the box-like structure.
 13. A granulator according to claim 11, said mounting means including elastomeric sHear mountings interconnecting the bottom of the base to the bottom of the box-like enclosure.
 14. A granulator according to claim 4, said box-like enclosure including a frame and panels removably attached to the frame. 